AU601217B2

AU601217B2 - Pump

Info

Publication number: AU601217B2
Application number: AU78639/87A
Authority: AU
Inventors: Michio Abe; Naoyuki Maeda; Ichiro Mizutani
Original assignee: Tokai TRW and Co Ltd
Current assignee: Tokai TRW and Co Ltd
Priority date: 1982-02-05
Filing date: 1987-09-17
Publication date: 1990-09-06
Anticipated expiration: 2003-02-03
Also published as: IT1162817B; GB8302973D0; ES8402394A1; NL8300461A; DE3303856C2; FR2521229A1; BE895828A; GB2116258A; DE3303856A1; AU7863987A; JPS58135391A; IT8367120A0; ES519562A0; AU1099883A

Description

I AUSTRALIA 6 Patents Act COMPLETE SPECIFICATION

(ORIGINAL)

Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority

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m~..My Related Art: APFLICANT'S REF.: FP/T-15-136 TOKAI TRW CO., LTD.

Div. of 10998/83 Name(s) of Applicant(s): Address(es) of Applicant(s): Actual Inventor(s): No. 1203, Aza Shimotamonaka, Ushiyama-cho, Kasugai-shi, Aichi-Ken, Japan.

Michio ABE.

Ichiro MIZUTANI Naoyuki MAEDA Address for Service is: Complete Specification for the invention entitled: PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000

PUMP

The following statement is a full description of this invention, including the best method of performing it known to applicant(s): P19/3/84 2

PUMP

This invention relates to improvemen in and relating to pumps and more particularly, to an oil pump adapted to pump pressurized oil to the power cylinder in a power steering device which assists a steering wheel in a vehicle, for example.

Generally, the oil pump employed in a power steering device of a vehicle is required to make minimum noise, stand against high load and enjoy long service life even when the pump is operated under a wide range number of rotations of the vehicular engine in an environment where high temperature and dust exist. In order to meet such t requirements, almost all conventional pumps are the vane pumps or their modified slipper vane pumps.

tf The slipper vane pump generally comprises a cam ring havincr a cam face on the inner surface thereof, side t C plates disposed on the opposite sides of the cam ring and having suction and discharge ports, a rotor positioned c in a sealed space defined by the cam ring and side plates for rotation therein and a plurality of slipper-vanes disposed about the outer surface of the rotor for slidable movement t in contact therewith. In the pump of the type as mentioned above, as the rotor rotates, oil is introduced through the suction ports into the sealed space to be compressed therein and the compressed oil is discharged through the discharge ports out of the pump. However, in order to maintain the efficiency of the pump high, the suction and discharge 3 ports and oil passages are complicatedly formed so that the pumping pressure can be adjusted. Therefore, the entire pump has a complicated construction and requires a substantial number of parts resulting in an expensive device.

And in the conventional pumps, since the cam ring and the side plates on the opposite sides of the cam ring all of which constitute the pump body are rigidly fastened together by rigid bolts, the pump has the disadvantage that when the pump body components expand or contract as the environment temperature varies and/or the pressure of oil being pumped changes, the rotor is subjected to an excessive i load or force, the rotor can not rotate smoothly. Furthermore, in the conventional pump, since both the opposite side plates have suction and discharge ports, when oil is sucked and discharged the cam ring and/or rotor are applied a great force to their opposite sides and the interface between the cam ring and rotor tends to wear severely which in turn makes a noise. In addition, in the conventional pump, oil seals are necessarily provided in spaces between the cam ring and the opposite side plates to prevent leakage of oil there and thus, the pump is required to be manufactured with a high precision and necessarily expensive. Still furthermore, in the conventional pump, when oil is discharged the opposite sideplates tend to move away from the cam ring and thus, spring means are required to urge the side plates against the cam ring resulting in a massive and expensive pump.

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According to the present invention there is provided a pump including a cam ring defining a pump chamber therein and having a cam face on the inner surface, a rotor disposed within said pump chamber and rotatable about a central axis, a plurality of slipper-vanes disposed about said rotor in slidable contact with said cam face on the cam ring, a suction side plate disposed on one side of said cam ring and having suction ports and a discharge side plate disposed on the other side of said cam ring and having a pair of outer arcuate discharge ports disposed about the central axis, a plurality of elastic bolts for fastenin( together said cam ring and suction and discharge side plates, a pair of inner arcuate discharge ports relatively smaller than and disposed about and more closely to the central axis than the outer discharge ports, a passage in communication with the outer and inner discharge ports and a cylindrical outlet in communication with the presage, whereby fluid flows from said suction side plate Lhrough said pump chamber to said discharge side pl~te.

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4-Ck r g: s 1 t when said fluid is pumped, saj means for urging the discharge side plate towards said am ring comprising the discharge ports provided on the di arge side plate and a passage The present invention will be more readily apparent to those skilled in the art from a reading of the following detailed description in conjunction with the accompanying drawings which show one preferred embodiment of the present invention for illustration purpose only, but not t

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MON.- I for limiting the scope of the same in any way.

Fig. 1 is a vertically sectional view of the pump embodying the principle of the present invention; Fig. 2 is a front elevational view 'bf said pump; Fig. 3 is a front elevational view of the cam ring in said pump; Fig. 4 is a side elevational view in partial section of said cam ring as shown in Fig. 3; Fig. 5 is a front elevational view of the suction side plate of said pump; S' Fig. 6 is a side elevational view in section of said suction side palte as shown in Fig. a Fig. 7 is a front elevational view of the discharge side plate of said pump; Fig. 8 is a side elevational view in section of s, id suction side plate as shown in Fig. 7; SFiq. 9 is a front elevational view of the reservoir tank in said pump; S 20 Fig. 10 is a side elevational view of said reservoir tank as shown in Fig. 9; Fig. 11 is a schematic view of the pump body as being received in said reservoir tank; Fig. 12 is a side elevational view of Fig. 11; Fig. 13 is an analytic diagram of stress applied to bolts which connect the components of the pump body together; Fig. 14 is a side view of one embodiment of the IL7 -6elastic bolt to be employed to connect the components of the pump body together; Fig. 15 is a side view of another embodiment of the elastic bolt to be employed to connect the components of the pump body together; and Fig. 16 is a detailed fragmentary view in section showing the relationshio between the elastic bolt and the pump body components fastened together thereby.

The present invention will be now described referring to the accompanying drawings and more particularly, St,) Fig. 1 thereof in which the entire pump embodying the 1 present invention is shown. The pump generally comprises s a pump body 1 and a reservoir tank 2 which receives the pump body 1 therein. The interior of the reservoir tank 12 is filled with fluid such as oil. The pump body 1 I comprises a cam ring 3, a suction side plate 4 on one side of the cam ring 3 and a discharge side plate 5 on the other or opposite side of the cam ring. The cam ring 3 has a center opening 6 the inner periphery of which is formed as a cam face which pumps the fluid in the conventional manner in cooperation with slipper-vanes of which description will be made hereinafter.

The center opening 6 in the cam ring 3 serves as a sealed pump chamber defined by the opposite suction and discharge side plates 4, 5 which are disposed on the opposite sides of the cam ring 3 in close contact therewith.

3 iJ The suction side plate 4 is disposed on one or the right-hand side o.f the cam ring 3 (as seen in Fig. 1) in close contact therewith and as more particularly shown i in Figs. 5 and 6* The suction side plate 4 comprises a larger diameter portion 7 and a smaller diameter portion 8, the latter of which is formed with a pair of larger arcuate outer suction ports 9, 9' and a pair of smaller arcuate inner suction ports 10, 10'. The smaller diameter portion of the suction side plate 4 is further formed with an inlet 11 which is in communication with the outer and inner arcuate suction ports 9, 9' and 10, The discharge side plate 5 is disposed on the other or left-hand side of the cam ring in close contact therewith (as seen in Fia. 1) and as more particularly shown ii 15 in Figs. 7 and 8. The discharge side plate 5 is formed with a pair of outer largcer arcuate discharge ports 12, 12', a pair of inner smaller arcuate discharqe ports 13, 13' and a cylindrical outlet 14 which is in communication with the outer and inner discharge ports. The discharge side plate 5 is formed with a passage 15 which is in communication with the outer and inner discharge ports. One end of the passage is open to the interface between the cam ring and discharge side plate.

The cam ring 3 includes a plurality of holes 16 (four holes in the illustrated embodiment) adjacent to the periphery of the ring in alignment with holes 17 in the discharge side plate 5 and similarly, the suction side plate is formed with the corresponding number of threaded I -8 holes 18 in alignment with the corresponding holes and in the discharge side plate and cam ring, respectively.

In assembling the components of the pump body to- I gether, elastic bolts 20 are first passed through the aligned holes in the cam ring and discharge side plate and then screwed into the threaded holes 18 in the suction side plate 4 whereby the suction and discharge side plates and cam ring are firmly connected together. In such a case, it is to be noted that no oil seals are provided between the suction and discharge side plates and the cam ring. Different embodiments of the elastic bolt 20 are in detail shown in Figs. 14 and 15. The elastic bolt shown in Fig. 14 has an intermediate elastic portion 21 between the head 22 and shank 23 of the bolt and the intermediate elastic portion 21 is designed to extend and contract by a suitable degree. In the illustrated embodiment, the elastic bolt is reduced in diameter in the intermediate elastic portion 21. In the embodiment shown in Fig. 15, the elastic portion 20 is externally threaded at' 24 to function as a coiled springr. The function of the intermediate elastic portion will be described hereinafter.

A rotor 30 is provided within the interior of the pump chamber. A plurality of slipper-vanes 40 are provided about the periphery of the rotor 30 in slidable contact with the cam face of the cam ring (see Fig. The slipper-vanes 40 are freely received in the corresponding recesses 31 formed in the periphery of the rotor 30 and 9 the slipper-vanes have contact faces 41 on their faces opposing to the cam face on the cam ring 3. A compression spring is interposed between the face of the slipper-vane remote from the cam face thereof and the bottom of the corresponding recess in the rotor 30 so as to always urgce the slipper-vane contact face against the cam face on the cam ring. As in i the conventional pumps, the pump of the invention is formed with the suction zone S and the discharge zone D (see Fig.

1 The suction ports in the suction side plate are positioned at the suction zone and similarly, the discharge ports in the discharge side plate are positioned at the discharge zone.

The slippers and rotor have such a width that they can be smoothly inserted into the spaces between the suction and discharge side plates. Although not shown, the rotor has a drive means such as a motor drive shaft i directly connected to the central area of the rotor.

In the illustrated embodiment of the pump, the rotor and drive shaft are connected together by means of serrations.

i 20 The motor drive shaft is journaled in a bearing 70 which are in turn provided on the motor mounting member The reservoir tank 2 comprises a plastic housing and has an opening 91 fitted on the larger diameter portion of the suction side plate 4 with an oil seal 90 interposed therebetween and an opening 92 fitted on the outer periphery of the discharge side plate 5 with an oil seal 93 interposed therebetween. The reservoir 2 further includeF an oil injection port 2a and an oil inlet 2b in IL, I 0 communication with the inlet in the suction side plate (see Figs. 9 and 10). Reference numeral 95 denotes a filter provided in the oil inlet. In this arrangement, the reservoir tank 2 receives the pump body 1 in sealing relationship.

In the pump described hereinabove, when the motor Sis rotated, the rotor 30 is rotated thereby whereby the slipper-vanes 40 slidably move along the cam face on the cam ring 3 so as to introduce the fluid or oil through the oil inlet, the inlet 2b in the reservoir tank 2 and the suction ports 9, 9' and 10, 10' in the suction side plate 4 into the seal space within the cam ring 3 at the suction zone S and compress the introduced oil which is in turn discharged through the discharge ports 12, 12' and 13, 13' and outlet 14 in the discharge side plate at the discharge area out of the pump body 1. It is to be noted that when the pump of the invention is applied to the steering device of a vehicle, for example, the number of rotations of the rotor is preferably set over at least three times as high as that of idling rotations of the vehicular engine.

Since the conventional pump for the power steering of a vehicle is driven by the engine, in order to exhibit the maximum capacity of the pump while the vehicle is parking or enters its garage, the pump is designed to provide a predetermined maximum pressure and a predetermined maximum displacement at 600 1,000 r.p.m. in proportion to the number of rotations at such a particular time and thus, notwithstanding the fact that the numberof ii rotations of the pump increases when the vehicular speed and accordingly, the engine rotation rate increases, a substantial portion of the displaced oil is released by a pressure regulation valve or drooper valve. Thus, when the pump rotates at a rate within the range of 600 1,000 the efficiency of the pump is high, but when the rotational rate of the pump is within the range of 1,000 8,000 the pump is not only low in efficiency, but the pump becomes expensive because the components of the pump should be formed of high quality materials by taking wear-resistance and durability called for the pump when operated at a high rotational rate into consideration within the range of 1,000 8,000 r.p.m.

On the other hand, the pump of the present invention i 15 is designed to preferably rotate at a rotational rate within the I range of 1,800 5,000 r.p.m. at an engine rotational rate within the range of 600 1,000 r.p.m. when the vehicle is parking or enters the garage and the rotation of the pump is stopped or redrced when the vehicle speed or engine rotational rate exceeds the range. Thus, the capacity of the cam ring of the pump body is one third one fifth J that of the component of the corresponding conventional pump. In the illustrated embodiment of the pump, the maximum frictional movement velocity of the slidable parts of the pump is only one sixth one eighth that of the corresponding parts in the conventional pump. In the pump of the invention, the maximum circumferential velocity of the slidable parts is 4.5 m/sec. whereas the IL-i 11 Imaximum circumferential velocit.., of the corresponding I parts in the conventional pump is 16 rn/sec. From the low circumferential velocity of the slidable parts in the I pump of the invention, it will be understood that the costs of the materials of the cam ring slipper-vanes arnd the suction and discharge side plates arid of heat-treatment and processing of these parts can be substantially reduced.

Thus, in the illustrated embodiment of the pump according to the present invention, the suction and discharge side plates are usually formed of light metal alloy such as aluminum or die cast aluminum and the cam ring and rotor are formed of sintered alloy not subjected to any specific I treatment (cementation) without difficulties.

i Figs. 11 and 12 are schematic views showing comn- 415 parison between the size of the pump of the invention I (with the reservoir tank) and that of the conventional Ipumps. The weight of the pump of the invention shown by Ireference character C is 0.4 kg whereas the weight of the pumps shown by reference characters A and B, esectveyis 3. gand 3.2 kg, respectively.

Fro thesq Figures, it will be understood that the pump C of the invention is quite smaller than the conventional pumps A, B.

One of the important preferred features of the present invention is that the cam ring 3 and the suction and discharge side plates 4, 5 have the holes by which these components are positioned in place and the elastic bolts 20 passing through these three components connect the components ,rn.

13 i~E together to thereby provide the pump body. As mentioned hereinabove, although the suction and discharge side plates can be formed of light metal alloy such as aluminum or die cast aluminum, since the aluminum, steel and sintered alloy components of the pump are fastened together in side-by-side relationship by means of the steel bolts, it is necessary to consider the possibility that the pump may suffer from a lowering in efficiency or suffer damage due to yielding and/or fatigue destruction of the components resulting from sudden changes in the fastening force caused by differences between the thermal expansion coefficients of the components.

At the same time, it is necessary to suitably absorb pulsation of the oil pressure caused by the pressure within the pump varying from 0 standard tmospheres to about 70 standard atmospheres. Fig. 13 is an analytic diagram showing stress applied to the elastic bolt employed for connecting the components of the pump according to the present invention.

C In this Figure, the broken lines show stress applied to the conventional bolt when the bolt is tightened and the solid lines show stress applied to the elastic bolt employed in the pump of the invention when the bolt is tightened.

In the illustrated embodiment of the pump of the invention, it is assumed that the pressure within the pump is 300 kg at normal temperature and the fastening force by each elastic bolt at normal temperature is 300 kg. Variations in the fastening force by the bolts are shown in the following S Table.

t Cr 4 t n rrnon rrlrrr I n rr r ,4 n~011 L. trl

TABLE

Fastening Fastening Fastening Difference External Energy force at force at force at in fastening force absorbed by normal -350C 1000C force at -35 0 C applied components temperature and 100 0 C to bolt fastened Stress applied to conventional 300 kg 242 kg 388 kg 146 kg 30 kg 45 kg bolt (kg/mm Stress applied elasti bolt (kg/rmm) i 15 As clear from the above-given Table, the elastic bolt is well within the elastic and fatigue limits designed for the bolt and stress applied to the aluminum contact face on the head of the bolt is also within the yielding and fatigue limits designed for the bolt whereby reliance in the strength of the elastic bolt can be substantially improved.

Fig. 16 is a fragmentary sectional view showing the relationship between the elastic bolt and the components fastened together by the bolt. When the pump is in its inoperative position or rotates at a low rotational A rate, that is, at a low pressure, the side plates are urged towards the rotor under the fastening force provided I by the bolt as shown by the dottedline a and on the other hand, when the pump is at a high pressure or rotating at a high rotational rate, the side plates move away from the rotor as shown by the solid line b to provide suitable clearances between the rotor and side plates whereby the pressurized oil is evenly applied to the interface between the. rotor and side plates so as to maintain the rotor and slippers in their neutral position. In this way, the r interface between the rotor and side plates can be protected against potential flaw, burn and wear and pulsation of oil pressure can be effectively absorbed.

Furthermore, this effect prevents the inclination of the rotor and slipper-vanes which may be otherwise caused by the differential pressure applied to the opposite sides of the rotor and slipper-vanes whereby the oil can flow in the one- 16way passage with a minimum resistance.

SFurthermore, since the pump body of the invention has no oil seal rings, the oil is allowed to leak through the areas of the components fastened together by the bolts, but the leaked oil is immediately recycled to the reservoir tank and thus, the efficiency of the pump will not be adversely affected by the leaked oil.

While only one embodiment of the invention has fi been shown and described in detail, it will be understood that the same is for illustration purpose only and not to be taken as a definition of the invention, reference being had for this purpose to the appended claims.

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Claims

1. A pump including a cam ring defining a pump chamber therein and having a cam face on the inner surface, a rotor disposed within said pump chamber and rotatable about a central axis, a plurality of slipper-vanes disposed about said rotor in slidable contact with said cam face on the cam ring, a suction side plate disposed on one side of said cam ring and having suction ports and a discharge side plate disposed on the other side of said cam ring and having a pair of outer arcuate discharge ports disposed about the central axis, a plurality of elastic bolts for fastening together said cam ring and suction and discharge side plates, a pair of inner arcuate discharge ports relatively smaller than and disposed about and more closely to the central axis than the outer discharge ports, a passage in communication with the outer and inner discharge ports and a cylindrical outlet in communication with the passage, whereby fluid flows from said suction side plate through said pump chamber to said discharge side plate.

2. A pump substantially as herein particularly described with reference to what is shown in the accompanying drawings. DATED: 20 March 1990 I 0aao 0 t N1* 0' PHILLIPS ORMONDE FITZPATRICK Attorneys for: 6 1 5 c TOKAI TRW CO., TD -17- K- VHF